Ultradian Rhythms

• (AO1) Define ultradian rhythms

  Occur more than once a day
• (AO1) What does the cycle alternate between? + explain

  REM (rapid eye movement) and NREM (non rapid eye movement)

  Consists of 5 stages

  Complete sleep cycle = 4 stages of NREM and 1 stage of REM. This repeats itself every 90 minutes throughout the night.

  Research using EEG has highlighted distinct brain wave patterns during different stages of sleep.
• (AO1) Explain stages 1 and 2

  'Light sleep' = brain wave patterns become slower and more rhythmic

  Starting with alpha then beta waves
• (AO1) Describe stages 3 and 4

  'Deep sleep' = slow wave sleep stage.

  Difficult to wake someone up.

  Associated with slower delta waves
• (AO1) State stage 5

  REM (or dream) sleep.

  Body = paralysed

  Brain activity resembles that of an awake person
• (AO1) Give another example of ultradian rhythm

  Appetite = or meal patterns in humans. Most eat 3 meals a day and appetite increases or decreases due to food consumption.
• (AO3) Give a limitation point about UR

  Point: Problem with studying sleep cycles is that the difference observed in people makes investigating patterns difficult.

  Evidence: Significant difference between ppts in terms of duration of each stage, particularly stage 3 and 4 (just before REM sleep).

  Evaluate: Demonstrates that there may be innate individual differences in UR, which means that it is worth focusing on differences during investigations into sleep cycle.
• (AO3) Give a limitation of UR

  Point: Ecological validity.

  Evidence: The way in which research is conducted may tell little about UR in humans. When investigating sleep patterns, ppts must be subjected to specific levels of control + attached to monitors that measure such rhythms.

  Evaluate: May be invasive for ppts, leading to sleep in a way that does not represent their usual sleep cycle. Makes investigating UR e.g. sleep cycle extremely difficult as lack of ecological validity could lead to false conclusions.
• (AO3) Give a strength of UR using case study

  Point: Randy Gardener showed flexibility in UR

  Evidence: 17yr old boy (researcher Willian Dement from Stanford Uni joined), wanted to beat the world record + investigate the effect of sleep deprivation on cognitive abilities. 8th January 1964 = stayed awake for 11 days. Experienced problems = blurred vision + disorganised speech. After slept 15 hours, but only recovered 25% of lost sleep.

  Evaluate: Highlights large degree of flexibility in terms of the different stages within sleep cycle + the variable nature of UR